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The purpose of this work was to establish the best particle size for recovering high yields of total phenolic compounds (TPC), total anthocyanin compounds(TAC) and total flavonoid compounds (TFC) from roselle (Hibiscus sabdariffa) by applying supercritical carbon dioxide (ScCO2). The extraction rate, diffusivity and solubility of yield in ScCO2 were also studied and calculated utilizing models. Pressure (10 and 30 MPa), temperature (40 and 60 °C), and particle size (250 µm < dp < 355 µm, 355 µm < dp < 425 µm and 425 µm < dp < 500 µm) were employed as variables in this experiment. The greatest recovery was 11.96% yield, 7.16 mg/100 g TAC, 42.93 mg/100 g TPC and 239.36 mg/100 g TFC under the conditions of 30 MPA, 40 °C and 250 µm < dp < 355 µm, respectively. The extraction rate of supercritical carbon dioxide in roselle extraction ranged from 5.19 E−03 to 1.35 E−03 mg/s fitted using the Esquivel model. The diffusivity coefficient of ScCO2 ranged from 2.17E−12 to 3.72E−11 mg/s2, as fitted by a single sphere model. The greatest solubility of global yield, TAC, TPC and TFC in ScCO2 was 1.50 g/L, 0.3 mg/L, 1.69 mg/L and 9.97 mg/L, respectively, with a particle size of 250 µm < dp < 355 µm. The smaller particle size of roselle provides the maximum bioactive compound recovery and solubility. Furthermore, the diffusivity and extraction of ScCO2 are increased by decreasing the particle size. Therefore, a smaller particle size is appropriate for roselle extraction by ScCO2 based on the experimental and modelling data. [ABSTRACT FROM AUTHOR]

Anthocyanins are one of the bioactive compounds in roselle that has many medicinal proposes. Anthocyanins are placed in the inner part of the roselle; therefore, combinations of two methods were applied to extract the anthocyanins. The first stage is employing supercritical carbon dioxide (ScCO2) to break the particle surface or outer layer of the roselle based on the total phenolic compounds (TPC) recovery, and the second step was to apply subcritical water extraction (SWE) for the extraction of anthocyanins. The objective is to determine the best conditions to obtain high yields of total anthocyanins compounds (TAC) from the roselle (Hibiscus sabdariffa) by employing a combination of ScCO2 and SWE. The optimal conditions of ScCO2 (first stage) were 19.13 MPa, 60 °C, and 4.31 mL/min, yielding 18.20%, and 80.34 mg/100 g TPC, respectively. The optimum conditions of SWE (second stage) were 9.48 MPa, 137 °C, and 6.14 mL/min, yielding 86.11% and 1224.61 mg/100 g TAC, respectively. The application of integrated ScCO2 and SWE proved successful in achieving high anthocyanins production and yield as compared to previous extraction methods. This approach may be used to extract the roselle with a greater anthocyanin's concentration than the prior method. [ABSTRACT FROM AUTHOR]

The optimization of red pigment anthocyanin from roselle (Hibiscus sabdariffa) by subcritical water extraction (SWE) has not been the topic of a scientific investigation. Therefore, the objective of this paper was to establish the optimal parameters for obtaining the maximum yield, total anthocyanin compounds (TAC), total phenolic compounds (TPC), and total flavonoid compounds (TFC) by SWE utilizing a response surface methodology. The optimal conditions were 8.75 MPa, 393.54 K, and 4.89 mL/min, with a yield of 0.69 g/g, TAC of 927.74 mg/100 g, TPC of 39.54 mg/100 g, and TFC of 614.57 mg/100 g. High temperatures and flow rates are favorable for achieving a maximum yield. In contrast, a high temperature is suitable for obtaining high concentrations of anthocyanin, flavonoid, and phenolic compounds. This technique (SWE) recovers anthocyanin at a greater extraction rate than traditional methods; hence, SWE may be substituted for conventional methods for extracting anthocyanin. [ABSTRACT FROM AUTHOR]

The purpose of this work was to determine the optimal conditions for recovering high yields of total phenolic compounds (TPC), total flavonoid compounds (TFC), and antioxidant activity (AA) from roselle (Hibiscus sabdariffa) by employing supercritical carbon dioxide (ScCO2). The solubility of yield, phenolic, and flavonoid in ScCO2 was estimated using solubility models. Pressure (10 to 20 MPa), temperature (40 to 60°C), and flow rate (3 to 5 ml/min) were used as factors in this investigation. According to the response surface methodology (RSM), the optimal conditions were 20 MPa, 40°C, and 4.875 ml/min, yielding 14.11%, 935.48 mgGAE/L TPC, 812.16 mgQUE/L TFC, and 98.59% antioxidant activity, respectively. With 5.29%, 1.28%, and 1.34% of average absolute relative deviation (AARD), the Putra model provided the best connection to the yield extract, phenolic, and flavonoid solubility. The use of RSM and modeling was effective in attaining a high production and concentration of phenolic compounds. Practical applications: Roselle (Hibiscus sabdariffa) comprises several beneficial components, including phenolic, flavonoid, and antioxidant substances. It is used to treat pyrexia, liver damage, hypertension, and leukemia, among other conditions. Toxic and conventional solvents, on the other hand, have often been utilized to recover these valuable compounds. To alleviate these disadvantages, the important chemicals in roselle are extracted using supercritical carbon dioxide (ScCO2). The solubility behavior of oil yield, phenolic, and flavonoid compounds was determined in this work using a semi‐empirical model. The data indicate that an endothermic process occurred to enhance the solubility of yield extract and the exothermic process is suitable for the phenolic and flavonoid recovery. [ABSTRACT FROM AUTHOR]